For me, as a founder of a young startup, the overarching benefit of being proficient in modern JS and sorrounding tooling is that I can use the same language for my whole stack(servers, web, Android, iOS), and spend more time thinking about the product and business. In the possible future where the company grows enough where it needs a distributed server software, the only part of the product that'd be changing would…
Not to mention the web stack changes every single year completely, node has scalability and versioning issues, and you end up relying on quickly changing pieces of code you have zero control about.